ADVANCED CONTAINMENT DESIGN TO ENHANCE PASSIVE SAFETY THROUGH PHORETIC DEPOSITION PHENOMENA Pittsburgh Technical LLC.

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1 ADVANCED CONTAINMENT DESIGN TO ENHANCE PASSIVE SAFETY THROUGH PHORETIC DEPOSITION PHENOMENA Pittsburgh Technical LLC. ANS PSA Meeting, 2017 Pittsburgh, PA

2 My Background 16 years Nuclear Engineering with Westinghouse and Pit-Tech Power Plant Component Analysis and Design: Reactor vessel head assemblies and steam generators Reactor coolant pumps and valves Lifting and handling devices Steam generators / Reactor Spent fuel pools Containment cooling systems Analysis: Structural, Fluids and thermal (CFD) Risk and Safety: Probabilistic Risk Assessments (PRA) Post-Fukushima reconciliation Fire hazard, seismic, reliability New build risk manager AP1000, SMR, System 80 Equipment Qualification and Testing: Environmental hazards assessment Academic Credentials: PhD, Risk Management, CMU MBA, CMU MSc, Mechanical Engineering, CMU BSc, Mechanical Engineering, University of Pittsburgh Certified Risk Professional

3 Background and Purpose of Research on Advanced Containment Vessel Design Purpose: Develop containment design guidance for advanced ipwrs for optimal passive decontamination through natural phenomena Significance: Available design guidance and correlations are for LLWRs, SMR-specific correlations must be empirically determined Benefit: SMR correlations should provide reduced design basis and beyond design basis accident source terms LLWR Post-Accident Aerosol Release and Mitigation: SMR Post-Accident Aerosol Release and Mitigation: No containment sprays to decontaminate post-accident aerosolized radionuclides Designs significantly rely on natural decontamination mechanisms: Thermophoresis Diffusiophoresis Gravitational settling 2

4 Understanding the Gaps in Nuclear Containment Decontamination Factors Source: Electric Power Research Institute 3

5 Understanding the Various Deposition Phenomena in the Respirable Range Respirable Range: Theoretical requirements for the simulant include a particle size within the respirable range, under 10 μm. Phenomenological Range: Aerosol gravitational settling deposition velocity is sensitive to particle size and applicable for particles above 1um in size 4

6 Design Optimization: Containment Vessel Surface Area to Free Volume Ratio is a Key Parameter Idealized approximation of the containment as concentric volumes, simplifies the estimation with the hot surface as the inner cylinder (reactor vessel) and cold surface as the outer cylinder (containment vessel). Condensation Saturated Super Heated Higher surface area to volume ratios: More deposition surface More condensation surface More efficient (radial) deposition directly from RV to CV wall Containment Vessel Wall Convective Diffusiophoresis + Thermophoresis + Gravitational Thermophoresis + Convective Reactor Vessel Wall Greater deposition velocities associated with condensation Greater significance for phoretic deposition: Diffusiophoresis is greater because of additional Stefan flow effect Thermophoresis is more significant because of higher thermal gradient (cold CV relative to hot bulk CV volume) 5

7 Design Optimization for Passive Decontamination Thermal Hydraulic Considerations Thermal hydraulic considerations include: Thermophretic driven deposition based on a thermal gradient Diffusiophoresis driven deposition based on a steam concentration gradient Condensation Convective flow Iterative Containment Vessel Wall 50psi 100psi Reactor Vessel Wall 6

8 Potentially Increased Phoretic Deposition Velocities associated with Immersed Containment Vessel Walls Smaller surface area to volume ratio, places the ipwr flow in the slip flow regime Increased particle interaction with the gas leading to Stefan flow, which is the convective flow of a condensing gas toward the cold surface, and carries the aerosol particles along by Stokes drag. 7

9 Summary Major Takeaways Demonstration of passive safety features are critical for advanced reactors because: Safety: The tradeoff with removal of some active cooling systems such as containment sprays, requires high confidence that the passive systems will compensate. Economics: Passive safety systems allow the opportunity for simpler and less expensive designs Licensing: Demonstration of passive safety supports a graded / right-sized regulatory framework 8

10 Project Team Members and Areas of Expertise Professor Paul Fischbeck Carnegie Mellon University Dr. Sola Talabi Pittsburgh Technical Dr. Tevfik Gemci Pittsburgh Technical Rohan Biwalkar Pittsburgh Technical Risk and uncertainty Mechanical Engineering, Risk Analysis Computational Fluid Dynamics, Aerosols Computational Fluid Dynamics Contact: Dr. Sola Talabi Pittsburgh Technical 9